Sound attenuation in long enclosures.

An intensive review indicates that among the existing formulae on the sound attenuation in long enclosures, only the geometrical reflection model seems relatively practical. Computations with this model show the following for rectangular long enclosures: with a larger cross-sectional size the relative attenuation from a given section is less but the absolute attenuation with reference to the source power is greater; the efficiency of absorbers is higher when there is less absorption; and obtain a higher attenuation, the absorbers should be evenly arranged in a section. In conclusion, it is still necessary to develop a more practical prediction method.